Nostalgia indeed! The look and feel is Mac OS 8!
About the docs: the README was babelfished from Japanese and is truly funny but less than useful. The html page is actually a proper translation and is quite clear on how to customize MLVWM. You can find it after installation at /usr/doc/mlvwm-0.91/html/mlvwm.html. Pull it up in a browser (Dillo works fine for this, BTW) and you can do quite a bit of customization to increase functionality.
There are sample application configuration files for Netscape, xterm, and kterm. Using the Netscape one as a sample you can create custom menus for various applications by taking application keybindings and translating them to menu items. The net result is that the various menus (i.e. View, Label) that are grayed out by default can function correctly for various apps, much as they did in Mac OS 8. If I find the time I may create a few for common VL 5.8 Standard apps and post an updated package later. I invite anyone who decides to play with this to create application configs and I'd be happy to include them in a future package.
Despite it's age this really is a neat WM.